include/urcu/uatomic/arm.h

   1 // SPDX-FileCopyrightText: 1991-1994 by Xerox Corporation.  All rights reserved.
   2 // SPDX-FileCopyrightText: 1996-1999 by Silicon Graphics.  All rights reserved.
   3 // SPDX-FileCopyrightText: 1999-2004 Hewlett-Packard Development Company, L.P.
   4 // SPDX-FileCopyrightText: 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5 // SPDX-FileCopyrightText: 2010 Paul E. McKenney, IBM Corporation
   6 //
   7 // SPDX-License-Identifier: LicenseRef-Boehm-GC
   8
   9 #ifndef _URCU_ARCH_UATOMIC_ARM_H
  10 #define _URCU_ARCH_UATOMIC_ARM_H
  11
  12 /*
  13  * Atomics for ARM.  This approach is usable on kernels back to 2.6.15.
  14  *
  15  * Code inspired from libuatomic_ops-1.2, inherited in part from the
  16  * Boehm-Demers-Weiser conservative garbage collector.
  17  */
  18
  19 #include <urcu/compiler.h>
  20 #include <urcu/system.h>
  21 #include <urcu/arch.h>
  22
  23 #ifdef __cplusplus
  24 extern "C" {
  25 #endif
  26
  27 /* xchg */
  28
  29 /*
  30  * Based on [1], __sync_lock_test_and_set() is not a full barrier, but
  31  * instead only an acquire barrier. Given that uatomic_xchg() acts as
  32  * both release and acquire barriers, we therefore need to have our own
  33  * release barrier before this operation.
  34  *
  35  * [1] https://gcc.gnu.org/onlinedocs/gcc-4.1.0/gcc/Atomic-Builtins.html
  36  */
  37 #define uatomic_xchg(addr, v)                           \
  38         ({                                              \
  39                 cmm_smp_mb();                           \
  40                 __sync_lock_test_and_set(addr, v);      \
  41         })
  42
  43 #ifdef __cplusplus
  44 }
  45 #endif
  46
  47 #include <urcu/uatomic/generic.h>
  48
  49 #endif /* _URCU_ARCH_UATOMIC_ARM_H */